Electrospinning is a well-established fiber fabrication technique distinguished by its cost-effectiveness, scalability potential, and exceptional processing versatility that allows to tailormade the final properties (e.g. surface wettability, porosity, surface area, mechanical properties and rugosity) of envisaged platform. The demand for advanced electrochemical platforms has increased, positioning electrospinning as a particularly attractive strategy for the development of future systems for electrochemical devices. Electrospun materials for electrochemical applications such as batteries, fuel cells, sensors and capacitors/supercapacitors allow the production of unique complex platforms, where their hierarchical fibrous architectures enable enhanced mass transport, charge transfer, and interfacial activity. This review provides a comprehensive and up-to-date overview of the basic principles of electrospinning technology comprising the different strategies to obtain fibers at micro/nano scale, morphologies, and chemical nature. The electrochemical application of electrospun systems comprising electroactive and/or dielectric materials is also reviewed in detail. Moreover, it addresses the future outlook of electrospinning technology regarding electrochemical devices and its challenges.

The widespread use of pharmaceuticals has led to increasing concern over the environmental persistence and biological risks of paracetamol (PA). Its frequent detection in surface and drinking water highlights the need for sensitive, rapid, and on-site detection methods. In this study, we present the first application of a surface acoustic wave (SAW) sensor for PA detection. The sensor is functionalized with a nanocomposite of titanium dioxide nanoparticles and carboxylated multi-walled carbon nanotubes, combining SAW’s high sensitivity with nanomaterial-based molecular selectivity. A fully integrated platform is developed, featuring a microfluidic sampling module and automated real-time phase response acquisition. The system exhibited a clear linear relationship between phase shift and the logarithm of PA concentration over a broad range (100 nM–1 mM), achieving a sensitivity of 0.9799°/decade (R² = 0.9995) and a limit of detection (LoD) of 28.6 nM. The response time reached 3.26 s, and the device demonstrated good repeatability (RSD = 6.53

Lung cancer is the most common cancer worldwide, responsible for more deaths per year than any other cancer, with non-small cell lung cancer (NSCLC) being the most prevalent form. Elevated epidermal growth factor (EGF) levels have been associated with NSCLC and decreased survival, highlighting its potential as a prognostic and predictive biomarker. This study proposes developing and validating a novel impedimetric electrochemical biosensor for the sensitive and accurate detection of EGF in serum samples from patients with lung adenocarcinoma. The biosensor was constructed by electropolymerization of polypyrrole nanotubes (PPy-NTs) on screen-printed carbon electrodes, followed by the deposition of carboxylated multiwalled carbon nanotubes (MWCNT-COOH) used for the immobilization of biorecognition elements. Anti-EGF antibodies were covalently immobilized on the MWCNT-COOH-modified surface, and bovine serum albumin (BSA) was used to block nonspecific interactions. Electrochemical impedance spectroscopy (EIS) was employed to characterize each fabrication step and to detect EGF. The biosensor demonstrated a wide linear detection range from 500 fg mL(-1) to 200 pg mL(-1) with high linearity (R-2 = 0.9924) and a remarkably low limit of detection (LOD) of 392 fg mL(-1). The developed biosensor demonstrated excellent agreement with ELISA results, with a strong Pearson correlation (r = 0.865, p < 0.0001), and Bland-Altman analysis with 97.4% of the differences within the limits of agreement. The biosensor successfully monitored changes in EGF levels in patients undergoing chemotherapy, showing a percentage change similar to that observed with ELISA. These results indicate that the developed impedimetric biosensor is a promising, sensitive, and reliable alternative for monitoring EGF levels in lung cancer patients, potentially aiding in prognosis and treatment evaluation

Electrolyte retention in electrolyte-gated transistors (EGTs) is typically achieved through viscous electrolytes or extra manufacturing steps for the reservoir design. In this work, we present a multifunctional solid-dopant matrix (SDM) composed of microfibrillated cellulose embedded with potassium chloride (MFC:KCl), which simultaneously acts as an electrolyte reservoir and provides ion anchoring that simplifies the device architecture and processing. For comparison, four electrolyte configurations were systematically investigated: (i) H2O (as a nonionic reference), (ii) MFC:H2O, (iii) KCl:H2O (as an ionic reference), and (iv) MFC:KCl:H2O. In water-based transistors, the MFC matrix serves as a pure electrolyte reservoir, showing water retention capability equivalent to the reference device, characterized by an on/off current ratio of ∼102, a threshold voltage of -0.13 V, a maximum drain current of ∼10-4 A, and a maximum transconductance of ∼0.5 mS, operating within a stable electrochemical window. In KCl-H2O-based transistors, the MFC:KCl material demonstrates dual functionality: simultaneously (i) retaining the electrolyte and (ii) compressing the operational electrochemical window (-0.2 to +0.8 V in MFC:KCl:H2O vs -0.9 to +1.0 V in KCl:H2O controls). This enables stable transistor operation up to V G ∼ -2 V while maintaining comparable current modulation (I on/I off ratios ∼ 103), against unstable operation of KCl:H2O electrolyte-based devices. In addition, it presents a threshold voltage of -0.7 V, a maximum drain current of ∼10-3 A, and a maximum transconductance of ∼ 3 × 102 mS. This study reveals that MFC offers a versatile platform for both field-effect and electrochemical transistors, aligning with green electronics initiatives by avoiding synthetic polymers like polydimethylsiloxane (PDMS).

One of the biggest environmental challenges of contemporary times is the increasing pollution of air, soil, and water by pesticides and hazardous metals. These contaminants persist in nature, accumulating through food chains, and endangering both ecosystems and human health. Large-scale environmental monitoring is restricted by the high cost, complex operation, and lack of portability of traditional analytical techniques, which are still the gold standard for accurate detection. In recent years, electrochemical sensors have emerged as a viable and powerful alternative. They combine sensitivity, selectivity and affordability with quick and on-site measurements. This review explores the main advances in electrochemical strategies for detecting pesticides and toxic metals, along with potentiometric, amperometric, voltammetric, and impedimetric approaches, as well as new hybrid systems that integrate optical and electrochemical detection. The impact of new materials, such as nanocarbons, metal and metal-oxide nanostructures, conducting polymers, and biofunctional interfaces are specifically highlighted. Combined, these innovations have enabled the creation of devices with ultra-low detection limits, high reproducibility, and the potential for real-time environmental monitoring. The review concludes by emphasizing how these technologies are advancing from laboratory research toward real-world applications, enabling faster, easier, and more sustainable pollutant detection for environmental preservation.

A high-performance electrochemical sensor for methyl parathion (MP) detection was developed using silver nanoparticles (AgNPs) integrated with graphene oxide/ionic liquid (GO/IL) on a screen-printed electrode (AgNPs@GO/IL@SPCE) for enhanced sensitivity and stability.

In this work, a polypyrrole nanotube/silica (PPyNT/SiO2)-modified electrode was prepared by an all-electrochemical route and characterized by electrochemical, spectroscopic, and microscopy analyses; scanning electron microscopy confirmed the superimposition of a particulate silica on the PPyNTs without any loss of electroactivity of conducting polypyrrole. The PPyNTs/SiO2 electrode was employed for the electroadsorption of caffeine, where it was found that in its less oxidized form, the PPyNTs boosted the adsorption capability of intrinsic silica. Electrochemical impedance spectroscopy (EIS) modeling was employed and modeled with equivalent circuit methodology, and all the results were compared with the Sips isotherm model, showing that the PPyNTs/SiO2 electrode presented a more heterogeneous surface (n S = 1.25) and a nearly 2-fold increase in maximum adsorption capacity (q ms) compared to pristine PPyNTs.

Sugarcane bagasse and exhausted black acacia bark biomass residues were pyrolyzed at high temperatures to obtain biochars with structures analogous to graphene oxide, as an economically viable destination for these waste materials. The biomasses were subjected to pretreatment with water and dilute nitric acid, followed by pyrolysis at 900 degrees C in an atmosphere of isopropanol vapor with N2. Additionally, pyrolysis was conducted under the same conditions without pretreatment (with isopropanol) and with only a nitrogen flow for comparison. The biochars obtained by pyrolysis with isopropanol presented lower H/C ratios, indicating high graphitization, and more stable O/C ratios, with characteristics of graphene-like material or graphene oxides. The biochars were used to modify electrodes, together with polyaniline (PANI). The electrodes modified with PANI and the biochars with isopropanol vapor showed specific capacitances (Cs) up to 2.7-fold higher than for the electrode modified with PANI alone, with the high Cs values maintained even after 1000 charge and discharge cycles, as well as significantly increased capacitive currents. Pyrolysis with isopropanol proved to be an effective and fast method that conferred different biochar characteristics, compared to the biochars produced by pyrolysis in N2 alone. These results are promising for the development of high-performance supercapacitors with low production costs.

The carcinogenic bacterium Helicobacter pylori infect over half the global population, with a higher prevalence in low-income countries. It is linked to diseases such as chronic gastritis, peptic ulcers, and gastric cancer, a leading cause of cancer-related deaths worldwide. The gold standard diagnostic method involves histopathological evaluation of gastric biopsy tissue via upper gastrointestinal endoscopy-an invasive, complex, and timeintensive procedure requiring specialized professionals. This study presents a noninvasive alternative: an impedimetric electrochemical biosensor for H. pylori antigen detection in saliva. The biosensor was developed using a screen-printed carbon electrode modified with polypyrrole nanotubes and carboxylated multi-walled carbon nanotubes. Monoclonal antibodies targeting CagA, a cytotoxic effector protein of H. pylori, were immobilized on carbon nanotubes using EDC/NHS chemistry. The platform was characterized via scanning electron microscopy and electrochemical techniques. Electrochemical impedance spectroscopy (EIS) was employed for analyte detection, with an analytical curve constructed in phosphate-buffered saline (PBS) spiked with CagA protein. The biosensor demonstrated a linear detection range of 0.5 pg mL 1 to 3.3 ng mL 1 and a detection limit of 109.9 fg mL 1 . Validation with patient saliva samples, confirmed by histopathology and rapid urease testing, yielded 97 % accuracy, 80 % sensitivity, and 100 % specificity. Results were obtained within 15 min. This EIS-based biosensor offers a sensitive, innovative, and noninvasive platform for early H. pylori diagnosis, which is essential for preventing severe diseases such as gastric cancer.

Flexible electrodes have attracted significant interest in the development of different electrochemical systems, especially in energy storage devices development. In this context, flexible supercapacitors are attracting attention by offering mechanical flexibility, light weight and optimal energy, and power densities to meet the demands of future innovations in wearable technology, smart textiles, and other flexible electronic applications. Nonetheless, effectively uniting low-cost electrode production with high performance is still a challenge. In this work, a new substrate based on pyrolyzed cotton fabric was developed using an atmosphere of N2 with benzaldehyde vapor during the pyrolysis process. The process resulted in the formation of a conductive fabric with graphitic characteristics, including high conductivity, as demonstrated by the reduction in sheet resistance from 2949 ± 2728 Ω sq−1 (measured in pyrolysis without benzaldehyde vapor) to 174 ± 67 Ω sq−1, in the pyrolysis process conducted with the atmosphere modifier. The fabric also exhibited a hydrophobic surface, with a mean contact angle of 118° ± 2, and featured interconnected fibers of untreated cotton. To enhance the electrochemical properties of the material, a simple methodology for one-pot chemical synthesis of AuNPs@PPy was proposed, where pyrrole monomer was used as the reducing agent, forming AuNPs capped by PPy with a mean diameter of 7 ± 2 nm. The material was characterized by scanning electron microscopy and transmission electron microscopy images, elemental mapping, Fourier-transform infrared spectroscopy, and electrochemical methods. The presence of the composite improved the specific capacitance of the electrode, obtaining a value of 30.4 mF cm−2 at a current density of 0.25 mA cm−2, presenting a forward-looking perspective on harnessing cotton fabric residues to construct eco-friendly high-performance devices, especially in supercapacitors development.

In this work poly(3,4-ethylenedioxythiophene) nanotubes (PEDOT-NTs) containing gold nanoparticles (AuNPs) were electrochemically synthesized and characterized in detail by using in situ Raman spectroelectrochemistry. Combining conducting polymers and metallic nanoparticles (AuNPs) enhanced conductivity and superficial area of PEDOT-NTs, key factors for electrochemical sensors. In order, to better understand the modified electrodes behavior, two different micropollutants, butylparaben and triclosan, were added onto the electrode surface and the spectroelectrochemical characterization was done. The Raman imaging showed that micropollutants adsorption increases the presence of partially oxidized segments in PEDOT nanotubes, showing that PEDOT-NTs/AuNPs modified electrodes has sensitivity to micropollutants presence. In this regard the electrochemical impedance spectroscopy characterization was performed and agrees with the spectroelectrochemical characterization results, in which the charge-transfer resistance increase proportionally with the micropollutants concentration. Therefore, the present work shows the potentiality of combining the unique characteristics of the PEDOT nanotubes decorated with AuNPs nanoparticles to develop devices for detection of organic molecules of environmental interest.

AbstractEnhancing the supercapacitors’ performance relies on the increased capacitance and voltage window, which are the current key challenges for developing new materials. In this study, the mononuclear NiII‐bis(oxamato) complex ([nBu4N]2[Ni(opba)], 1) has been synthesized and used as a template in polypyrrole (PPy) based conductive polymer as a novel electrode material for supercapacitor applications. The surface and structural properties of PPy and PPy/1 electrodes were studied using SEM and TEM to elucidate their interactions. The results of characterization techniques revealed that complex 1 altered the morphology, creating a prominent three‐dimensional globular structure in the PPy/1 hybrid material without significant chemical modification. The electrochemical properties of PPy and PPy/1 were investigated by CV, EIS, and GCD analyses. The PPy/1 electrode demonstrated intense pseudocapacitive behavior, showing a significantly widened potential window and increased current compared to the PPy electrode, resulting in enhanced energy storage capacity within the material. This improvement was evaluated by testing a symmetric supercapacitor in a coin cell architecture with an alginate‐based gel acting as both electrolyte and separator. The maximum specific cell capacitance reached 41.6 F g−1 at a current density of 0.2 A g−1, with a remarkable capacity retention of 97 % after 1000 galvanostatic charge/discharge cycles.

Supercapacitors (SCs) are promising energy storage devices exploited for emerging technologies including electric and hybrid cars, and have also gained increasing interest in portable and flexible electronic devices. They are usually divided according to the storage mechanism into electrical double-layer capacitors and pseudocapacitors. Also, according to the cell configuration, supercapacitors can be constructed symmetrically or asymmetrically. Asymmetric SCs stand out as configurations with a larger potential window, and therefore, better values of power and energy density, compared to symmetrical devices. Among the asymmetric devices, hybrid capacitors are promising devices due to their high energy density, acquired by the battery-type electrode, without losing the good cyclicality of capacitive devices. In addition, supercapacitor architecture influences their final performance and should be considered according to the purpose of the application. The major cell architectures are discussed in this chapter, such as coin cell, pouch cell, and cylindrical cell, as well as the main market trends for asymmetric and hybrid supercapacitors.

The present work shows the electrocatalytical performance of nickel/cobalt alloys towards the conversion of glycerol into higher value molecules, such as glycolic acid, oxalic acid, maleic acid, diethylene glycol and ethylene glycol, identified by chromatographic technique. To do so, the alloy was directly electrodeposited on graphite electrodes, which is a simple, readily available and cheap material, the modified electrodes were characterized by scanning electron microscopy, infrared spectroscopy and electrochemical analysis. Kinetic parameters were obtained using by both Galus methodology and rotating disc electrode (RDE), obtaining the better electrocatalytic modified electrode and the total number of electrons transferred per mol of glycerol. The modified electrode labeled as Ni0.8Co0.2(OH)(2) proportion has achieved the highest glycerol conversion after 4 h of reaction, approximately 99.8%, with an energy consumption of 36.38 W/mol.

In this work we show the electrosynthesis of poly(pyrrole) films in the presence of SiO2 nanoparticles to develop a hybrid electrode to study the adsorption properties based on the electrochemical and interfacial features of the modified electrode. The electrodes were carefully characterized using electrochemical techniques such as voltammetry and electrochemical impedance spectroscopy, demonstrating that the inclusion of SiO2 nanoparticles in the PPy films has improved the electroactivity of the conducting polymer, in terms of both kinetics and mass transport. The morphology of the electrodes was also investigated by scanning electron microscopy, demonstrating the high surface achieved by the electrodeposition of either PPy and PPy/nano-SiO2. The system was studied for the electroadsorption of caffeine where the applied potential at the substrate plays a key role in tax of the adsorbed specie, mostly due to the increase of van der Waals interactions, enhanced greatly by the presence of the SiO2 nanoparticles. Adsorption isotherms and modeled equivalent circuits were also adopted to further characterize the interfacial properties of the different electrodes synthesized herein.

This short review presents the latest advances in the field of electrochemical biosensors, focusing particularly on impedimetric biosensors for the direct measurement of analytes. As a source of study we have chosen to describe these advances in the latest global health crisis originated from the COVID-19 pandemic, initiated by the SARS-CoV-2 virus. In this period, the necessity for swift and precise detection methods has grown rapidly due to an imminent need for the development of an analytical method to identify and isolate infected patients as an attempt to control the spreading of the disease. Traditional approaches such as the enzyme-linked immunosorbent assay (ELISA), were extensively used during the SARS-CoV-2 pandemic, but their drawbacks, including slow response time, became evident. In this context, the potential of electrochemical biosensors as an alternative for COVID-19 detection was emphasized. These biosensors merge electrochemical technology with bioreceptors, offering benefits such as rapidity, accuracy, portability, and real-time result provision. Additionally, we present instances of electrochemical biosensors modified with conductive polymers, eliminating the necessity for an electrochemical probe. The adaptability of the developed materials and devices facilitated the prompt production of electrochemical biosensors during the pandemic, creating opportunities for broader applications in infectious disease diagnosis.

Helicobacter pylori (H. pylori) is classified as a class I carcinogen that colonizes the human gastrointestinal (GI) tract. The detection at low concentrations is crucial in combatting H. pylori. HopQ protein is located on H. pylori's outer membrane and is expressed at an early stage of contamination, which signifies it as an ideal biomarker. In this study, we presented the development of an electrochemical impedimetric immunosensor for the ultra-sensitive detection of HopQ at low concentrations. The sensor employed polypyrrole nanotubes (PPy-NTs) and carboxylated multi-walled carbon nanotubes (MWCNT-COOH) nanocomposite. PPy-NTs were chosen for their excellent conductivity, biocompatibility, and redox capabilities, simplifying sample preparation by eliminating the need to add redox probes upon measurement. MWCNT-COOH provided covalent binding sites for HopQ antibodies (HopQ-Ab) on the biosensor surface. Characterization of the biosensor was performed using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), contact angle measurements, and electrochemical impedance spectroscopy (EIS), complemented by numerical semiempirical quantum calculations. The results demonstrated a dynamic linear range of 5 pg/mL to 1.063 ng/mL and an excellent selectivity, with the possibility of excluding interference using EIS data, specifically charge transfer resistance and double-layer capacitance as multivariants for the calibration curve. Using two EIS components, the limit of detection is calculated to be 2.06 pg/mL. The biosensor was tested with a spiked drinking water sample and showed a signal recovery of 105.5% when detecting 300 pg/mL of HopQ. This novel H. pylori biosensor offers reliable, simple, portable, and rapid screening of the bacteria.